[KUDU-3047] Implement automatic selection of the time source for Kudu

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.12.0
• Labels: clock
• Target Version/s: 1.12.0
• Code Review: http://gerrit.cloudera.org:8080/15161
• Assignee: Alexey Serbin
• Reporter: Alexey Serbin
• Created: 03/Feb/20 17:44
• Updated: 18/Feb/20 17:32
• Resolved: 18/Feb/20 17:32

Description

With KUDU-2936 and KUDU-3009 implemented, it's now possible to automatically select time source for Kudu masters and tablet servers. Assuming Kudu is not going to be deployed in hybrid environments (like half of the cluster in GCE, another in Azure), it looks like a reliable way to get the same time source auto-selected across a Kudu cluster.

A few principles of the time source auto-selection are the following:

• in well recognized environments guaranteed to provide dedicated NTP service, use the provided NTP server(s) for the built-in client, so it's not necessary to require NTP server running at Kudu nodes
• in well recognized environments known not to provide NTP service, require the clock to be synchronized by an external NTP daemon
• report on the selected time source when the diagnostic tooling is run, showing warnings if the time source happen to set different for different tablet servers in the cluster

use the built-in client with information provided by DHCP (if any),

In detail:

• AWS: use built-in; run the built-in NTP client auto-configuration, if enabled
• GCE: use built-in; run the built-in NTP client auto-configuration, if enabled
• Azure: use system; optionally try to configure the built-in client using the information on NTP servers provided via DHCP for the host
• not recognized as cloud environment: use system; optionally try to configure the built-in client using the information on NTP servers provided via DHCP for the host